A stereo camera, also called dual camera, is a type of camera with two or more lenses with a separate image sensor for each lens. This allows the camera to simulate human binocular vision, gives it the ability to capture three-dimensional images, a process known as stereo photography. In smartphone technology, a stereo camera is commonly referred to as a dual camera for capturing both still images and videos.
In 2011, dual/stereo cameras were introduced in HTC smartphones to capture 3D images. Since then, smartphone manufacturers kept experimenting with the technology, but it never really took off. In 2014, HTC re-introduced its Duo camera setup and its improved depth of field effect. In 2016, dual cameras have evolved to deliver excellent results in modern smartphones. A dual camera can help in getting a sharper image with more details, enable an ultra-wide-angle mode or simply take photos with a shallow depth of field to make the subject more stand out. The dual camera setup can also add 1× or 2× optical zoom to the phone.
In some stereo cameras, such as the Mastcam imagers onboard the Mars rover Curiosity, the smartphone dual camera technology has not been practically applied. Some of the obstacles are the much more involved algorithms required and the cost of implementing such system in the Mastcam imagers. The left and right cameras of the Mastcam imager usually have different resolutions. Moreover, the cameras are not calibrated for stereo image formation, as they normally work independent of each other.
To generate stereo images from these two cameras with different resolutions, a common practice is to downsample the high resolution camera image to the same as the lower one. After that, the stereo images are formed by following some standard procedures. It is known that the downsampling of the high resolution camera image is more economical but less effective, as the resulting stereo images will have lower resolution. The resulting depth map derived from the resulting stereo images also has a low resolution.